1. Field of the Invention
The present invention relates to a drive unit for use in an optical memory device which records and/or reproduces information by using optical beam.
2. Description of the Related Art
In a conventional drive unit for use in an optical memory unit which uses optical disks or photoelectro-magnetic disks, a front panel with a cassette slot is attached to a deck unit which has a spindle motor to rotate a disk, a pick-up to record/reproduce the information to the disk, a motor to drive the pick-up in the radial direction of the disk, and an automatic load/eject mechanism to load a cassette containing a disk into the deck unit through the cassette slot, and to unload the cassette from the deck unit through the cassette slot.
In order to improve the drive unit, various efforts have been made. For example, the Japanese Patent Unexamined Publication No. 64-43888 proposes a drive unit, in which the front surface having a cassette slot is provided with an air vent. To the air vent air is supplied by a cooling fan from the slot via the back surface of a cassette case thereby to lower the temperature in the device unit.
In the conventional drive unit as mentioned above, since the back surface of the cassette case is used as a part of the air passage, the dust entering from the outside adheres to the disk in the cassette case, and also to the various optical components of an optical head. The dust decreases the quantity of light, making it difficult to record or reproduce information accurately or stably.
To solve this problem, a high-performance filter with high dust collecting efficiency can be installed at the air vent, through which the outside air is admitted, for collecting dust so that the drive unit can be cooled with clean air. However, the filter causes a pressure loss of air, requiring a large-capacity cooling fan. The use of a high-performance filter will result in high costs. As the filter is used over an extended period of time, the cooling air volume reduces due to filter clogging, increasing the possibility of a temperature rise in the drive unit. Consequently, the filter must be replaced by a new one, periodically or as required according to filter condition. This makes it difficult to design a drive unit which needs no maintenance for long time (for example, over 5 years).
However, similar adhesion of dust to disks and optical parts generally occurs even in the unit whose interior is naturally cooled through the vent without using a cooling fan.
In order to remove a cassette, which is held in the deck unit due to power failure or trouble in the eject mechanism, a manual eject mechanism such as a manual rotating means is installed to manually rotate an eject motor, as is disclosed in Published Unexamined Japanese Utility Model Application No. 63-40857.
However, in the conventional drive unit having a manual eject mechanism, the front panel is fixed to the deck-unit holding frame with screws or with pressure-sensitive, double coated adhesive tape. Consequently, in the case where the control section of the manual eject mechanism is located inside the front panel, it is hard and time-consuming to remove the front panel. Hence, it is impossible to unload a cassette immediately from the deck unit in case of power failure or trouble of the eject mechanism. The front panel may easily be broken during the removal of the cassette.
To solve these problems, an opening can be formed in the front panel, to operate the control section from the outside. This, however, jeopardizes the outer appearance of the product.
As described above, a slot is made in the front panel of the drive unit, to insert a cassette or a cartridge into the drive unit. In addition, a front cover is used to close the slot, thereby to prevent the entry of dust into the unit.
For example, in the information processor disclosed in Published Unexamined Japanese Patent Application No. 63-259864 or Published Unexamined Japanese Patent Application No. 60-93665, the slot is opened and closed with one front cover. The front cover rotatably opens to the inside when a cartridge is inserted into the slot and when the cartridge is set in the unit, the front cover completely closes the slot. When the cartridge is ejected, the front cover rotatably opens to the inside, as the eject mechanism function.
However, to open and close the slot, the front cover needs to rotate, occupying a large space for the motion. Hence, a wasteful space must be left in the unit, increasing the size of the unit.
Therefore, in an attempt to minimize the space required to allow the front cover to rotate, in the unit disclosed in Published Unexamined Japanese Patent Application No. 1-118283, two front covers of equal rotation radius are installed at the top and the bottom, respectively, of the slot, forming a folding door. The case of this folding door can reduce the space required to open and close the front cover.
However, since the two front covers have the same rotation radius, the tip ends of the front covers may bump into each other or overlap reversely to fail to achieve proper closing of the slot. Consequently, in the unit disclosed in Published Unexamined Japanese Patent Application No. 1-118283, the rotating phases of two front covers are varied by varying the number of teeth of front cover driving gears.
However, it is strongly demanded that an information processor like an optical disk unit be made smaller.
In the device disclosed in Published Unexamined Japanese Patent Application No. 1-118283, several gears are used to vary the rotating phases of two front covers as well as solenoids to drive these gears. This involves defects in that the configuration generally becomes complicated and the cost increases.
On the other hand, in the device disclosed in Published Unexamined Japanese Patent Application No. 60-93665, the front cover is rotated by a cam connected to a loading plate which moves in the horizontal direction only, during cartridge transportation. In the device disclosed in Published Unexamined Japanese Patent Application No. 63-259864, the front cover is rotated by a rotor which has a shaft extending parallel to the horizontal transportation direction. These front cover driving systems, are useless unless they have a specific transportation mechanism.